The present invention relates to pump seals, and more particularly, to a labyrinth seal for sealing an impeller shaft within a pump housing.
Labyrinth seals are known devices used in sealing an element such as a rotary shift to inhibit undesired fluid flow past the shaft. The usual labyrinth seal, when incorporated with a pump, is relied upon to inhibit leakage along the shaft of the fluid being pumped by the pump. Unlike seals of this type, the labyrinth seal of the instant invention is intended to be incorporated with a centrifugal pump with an important function of the seal being to prevent leakage of air into the pump during the time that the pump is being primed.
When incorporated with a centrifugal pump for pumping a fluid such as water the seal of the invention, therefore, not only impedes the flow of water along the impeller shaft of the pump when the pump is pumping water, but also impedes the flow of air inwardly along the impeller shaft during periods when the pump is being primed.
Accordingly, one object of the present invention is to provide a labyrinth seal for sealing an impeller shaft in a centrifugal pump housing, where the seal restricts air flow into the pump during pump priming, and restricts water leakage out of the pump during normal pumping.
A more specific object of the invention is to provide for use in such a pump, a seal having a greater resistance to fluid flow in a direction extending toward the impeller of the pump.
Still another object of the present invention is to provide such a seal which is easily adjusted to obtain proper clearances therein.
With these objects in mind, the present invention in labyrinth seal includes inner and outer coaxial, relatively rotatable members which are adapted to be secured to the shaft and housing, respectively, in a pump. The two members have walls defining therebetween axially extending, sleeve-shaped passages of decreasing diameters progressing toward the interior of the pump. The passages are connected at their adjacent ends by radially extending disc-shaped passages. Formed in the outer and inner members are annular grooves into which fluid moving through the sleeve-shaped and disc-shaped passages flows, to set up fluid currents which resist fluid flow through the seal.